Hidden diversity in the genus Tethya: comparing molecular and morphological techniques for species identification

Sponge functional roles in a changing world

Sponges are ecologically important benthic organisms with many important functional roles. However, despite increasing global interest in the functions that sponges perform, there has been limited focus on how such functions will be impacted by different anthropogenic stressors. In this review, we describe the progress that has been made in our understanding of the functional roles of sponges over the last 15 years and consider the impacts of anthropogenic stressors on these roles. We split sponge functional roles into interactions with the water column and associations with other organisms. We found evidence for an increasing focus on functional roles among sponge-focused research articles, with our understanding of sponge-mediated nutrient cycling increasing substantially in recent years. From the information available, many anthropogenic stressors have the potential to negatively impact sponge pumping, and therefore have the potential to cause ecosystem level impacts. While our understanding of the importance of sponges has increased in the last 15 years, much more experimental work is required to fully understand how sponges will contribute to reef ecosystem function in future changing oceans.

Another plea for 'best practice' in molecular approaches to trematode systematics: Diplostomum sp. clade Q identified as Diplostomum baeri Dubois, 1937 in Europe

DNA sequence data became an integral part of species characterization and identification. Still, specimens associated with a particular DNA sequence must be identified by the use of traditional morphology-based analysis and correct linking of sequence and identification must be ensured. Only a small part of DNA sequences of the genus Diplostomum (Diplostomidae) is based on adult isolates which are essential for accurate identification. In this study, we provide species identification with an aid of morphological and molecular (cox1, ITS-5.8S-ITS2 and 28S) characterization of adults of Diplostomum baeri Dubois, 1937 from naturally infected Larus canus Linnaeus in Karelia, Russia. Furthermore, we reveal that the DNA sequences of our isolates of D. baeri are identical with those of the lineage Diplostomum sp. clade Q , while other sequences labelled as the ‘D. baeri’ complex do not represent lineages of D. baeri. Our new material of cercariae from Radix balthica (Linnaeus) in Ireland is also linked to Diplostomum sp. clade Q. We reveal that D. baeri is widely distributed in Europe; as first intermediate hosts lymnaeid snails (Radix auricularia (Linnaeus), R. balthica) are used; metacercariae occur in eye lens of cyprinid fishes. In light of the convoluted taxonomy of D. baeri and other Diplostomum spp., we extend the recommendations of Blasco-Costa et al. (2016, Systematic Parasitology 93, 295–306) for the ‘best practice’ in molecular approaches to trematode systematics. The current study is another step in elucidating the species spectrum of Diplostomum based on integrative taxonomy with well-described morphology of adults linked to sequences.

De novo transcriptome assembly for two color types of the marine sponge Mycale (Carmia) cecilia

Despite the ecological importance and the potential pharmacological application of the sponge Mycale (Carmia) cecilia, it is uncertain whether the body-color variation, even in individuals coexisting in the same area, is due to intraspecific phenotypic plasticity or corresponds to taxonomic divergence. This uncertainty is relatively common in several Porifera groups, which lack the resolution of morphological diagnostic characters and slow-evolving mitochondrial genomes as occurs in early splitting lineages. We sequenced the RNA of six individuals with two different body-color (green-morphotype and red-morphotype) collected at the same time side by side. High-throughput sequencing of cDNA libraries produced ~ 129 million reads with a length of 150 bp. Each morphotype was assembled separately owing to the low overlapping in the global assembly. Metatranscriptome de novo assembly of the trimmed and normalized reads produced 461 thousand transcripts for the green-morphotype and 342 thousand for the red-morphotype (respectively). Over 30% of the transcripts contained Open Reading Frames (ORFs) with functional significance. BUSCO analysis of the ORFs of putative poriferan origin (31.3% green or 30.4% red) indicated that our assemblies are 60% complete. This is the first attempt to evaluate the morphological diversity in the species M. (C.) cecilia and the phylum Porifera at the transcriptomic level. Due to the minimum overlap of the assembly and that, the red-morphotype diverged significantly from the green-morphotype (original color of M. (C.) cecilia). Therefore, we suggest that the red-morphotype should undergo a complete taxonomic investigation and its taxonomic status be reviewed. We expect that the transcriptome assembly metrics can be useful for comparing other transcriptome assemblies of non-model organisms.

Seasonally Driven Sexual and Asexual Reproduction in Temperate Tethya Species

Marine organisms that rely on environmental cues for reproduction are likely to experience shifts in reproductive phenology and output due to global climate change. To assess the role that the environment may play in the reproductive timing for temperate sponges, this study examined sexual and asexual reproduction in New Zealand sponge species (Tethya bergquistae and the Tethya burtoni complex) and correlated reproductive output with temperature, chlorophyll-a concentration, and rainfall. Histological analyses of sponges collected monthly (from February 2015 to February 2017) revealed that these sponges are oviparous and gonochoristic and that they sexually reproduce annually during the austral summer. Both monthly collections and in situ monitoring revealed that Tethya spp. asexually bud continuously, but with greater intensity in the austral spring and summer. Temperature was positively associated with both sexual reproduction and budding, with seasonal cues appearing important. Future shifts in the environment that alter such cues are expected to affect population dynamics of these sponges.

Molecular and morphological congruence of three new cryptic Neopetrosia spp. in the Caribbean

Neopetrosia proxima (Porifera: Demospongiae: Haplosclerida) is described as a morphologically variable sponge common on shallow reefs of the Caribbean. However, the range of morphological and reproductive variation within putative N. proxima led us to hypothesize that such variability may be indicative of cryptic species rather than plasticity. Using DNA sequences and morphological characters we confirmed the presence of three previously undescribed species of Neopetrosia. Morphological differences of each new congener were best resolved by partial gene sequences of the mitochondrial cytochrome oxidase subunit 1 over nuclear ones (18S rRNA and 28S rRNA). Several new characters for Neopetrosia were revealed by each new species. For example, N. dendrocrevacea sp. nov. and N. cristata sp. nov. showed the presence of grooves on the surface of the sponge body that converge at the oscula, and a more disorganized skeleton than previously defined for the genus. N. sigmafera sp. nov. adds the (1) presence of sigma microscleres, (2) significantly wider/longer oxeas (>200 μm), and (3) the presence of parenchymella larvae. Sampling of conspecifics throughout several locations in the Caribbean revealed larger spicules in habitats closer to the continental shelf than those in remote island locations. Our study highlights the importance of integrating molecular and morphological systematics for the discrimination of new Neopetrosia spp. despite belonging to one of several polyphyletic groups (families, genera) within the current definition of the order Haplosclerida.